Travertine
, Yellowstone National Park]] Travertine (in other languages: Chinese: 洞石, Persian: تراورتن, German: Travertin) is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan and cream-colored varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter it can form stalactites, stalagmites and other speleothems. It is frequently used in Italy and elsewhere as a building material. Travertine is a terrestrial sedimentary rock, formed by the precipitation of carbonate minerals from solution in ground and surface waters, and/or geothermally heated hot-springs.Dictionary of Geological Terms, 1962. A Dolphin Reference BookA Glossary of Karst Terminology, 1970. Geol. Surv. Water-Supply Paper 1899-K, U. S. Gov. Print. Off., Washington. Similar (but softer and extremely porous) deposits formed from ambient-temperature water are known as tufa. Features Travertine forms the stalactites and stalagmites of limestone caves, and the filling of some veins and hot spring conduits. Travertine forms from geothermal springs and is often linked to siliceous systems which form siliceous sinter. Macrophytes, bryophytes, algae, cyanobacteria and other organisms often colonise the surface of travertine and are preserved, giving travertine its distinctive porosity. Some springs have temperatures high enough to exclude macrophytes and bryophytes from the deposits, consequently, deposits are generally less porous than tufa. Thermophilic microbes are important in these environments and stromatolitic fabrics are common. When deposits are apparently devoid of any biological component, they are often referred to as calcareous sinter. Geochemistry Modern travertine is formed from geothermally heated supersaturated alkaline waters, with raised pCO2 (see partial pressure). On emergence, waters degas CO2 due to the lower atmospheric pCO2, resulting in an increase in pH. Since carbonate solubility decreases with increased pH,Bialkowski, S.E. 2004. Use of Acid Distributions in Solubility Problems. http://www.chem.usu.edu/~sbialkow/Classes/3600/alpha/alpha3.html precipitation is induced. Supersaturation may be enhanced by factors leading to a reduction in pCO2, for example increased air-water interactions at waterfalls may be important,Zhang, D. Zhang, Y. Zhu, A. and Cheng, X. 2001. Physical mechanisms of river waterfall tufa (travertine) formation. Journal of Sedimentary Research '''71, pp. 205-216. as may photosynthesis.Riding, R. 2000. Microbial carbonates: the geological record of calcified bacterial-algal mats and biofilms. ''Sedimentology '''47, pp. 179-214. Precipitation may also be enhanced by evaporation in some springs. Both calcite and aragonite are found in hot spring travertines, aragonite is preferentially precipitated when temperatures are hot, while calcite dominates when temperatures are cooler.Pentecost, A. 2005. ''Travertine. Dordrecht, Netherlands: Kluwer Academic Publishers Group. ISBN 1-4020-3523-3Fouke, B.W. Farmer, J.D. Des Marais, D.J. Pratt, L. Sturchio, N.C. Burns, P.C. Discipulo, M.K. 2000. Depositional facies and aqueous-solid geochemistry of travertine-depositing hot springs (Angel Terrace, Mammoth Hot Springs, Yellowstone National Park, U.S.A.). Journal of Sedimentary Research '''70', pp. 565-585. When pure and fine, travertine is white, but often it is brown to yellow due to impurities (other than carbonate minerals). . Photo by Ansel Adams, 1941.]] Travertine may precipitate out directly onto rock and other inert materials as in Pamukkale or Yellowstone for example. Travertine may also precipitate out onto growing moss as happens a great deal in Plitvice Lakes. Occurrence Travertine waterfalls exist not only in the U.S. in Oklahoma and Texas but most famously in Tivoli, Italy and Guidonia Montecelio, near Rome. Travertine derives its name from this town. Tivoli was known as Tibur in ancient Roman times. The ancient name for the stone was ''lapis tiburtinus, meaning tibur stone, which has been corrupted to travertine. Detailed studies of the Tivoli and Guidonia travertine deposits revealed diurnal and annual rhythmic banding and laminae, which have potential use in geochronology. Folk, R. L., et al.; (1985) Bizarre forms of depositional and diagenetic calcite in hot spring travertines, in Carbonate Cements; SEPM Special Pub. 36. These formations commonly occur in tropical and subtropical karst areas around the world. In Central Europe's last postglacial palaeoclimatic optimum (Atlantic Period, 8000-5000 B.C.), huge deposits of tufa formed from karst springs. Important geotopes are found at the Swabian Alb, mainly in valleys at the foremost northwest ridge of the cuesta, in many valleys of the eroded periphery of the karstic Franconian Jura, at the northern Alpine foothills, and the northern Karst Alps. On a smaller scale these karst processes are still working. Travertine was a very important building material for housing and representative buildings since the Middle Ages. Travertine has formed sixteen huge, natural dams in a valley in Croatia known as Plitvice Lakes National Park. The travertine clings to moss and rocks in the water, and has built up over several millennia to form waterfalls up to 70 m in height.Nature . Land Of The Falling Lakes | Pbs Other beautiful cascades of natural lakes formed behind travertine dams can be seen in Mahallat, Abbass Abad, Atash Kooh (Iran), Band-i-Amir (Afghanistan), HuangLong Valley (Sichuan, China), Semuc Champey (Guatemala), and Pamukkale (Turkey). Many geyser fields also have colorful travertine deposits. In the U.S., the most well-known place for travertine formation are the geothermal areas of the Yellowstone National Park, which are rich in travertine deposits. In Oklahoma, there are two parks dedicated to this natural wonder. Turner Falls, the tallest waterfall in Oklahoma and one of the tallest in the U.S., is a 77-foot turquoise cascade of spring water flowing over a travertine cave under which one can swim. Honey Creek feeds this waterfall and creates miles of travertine shelves both up and downstream. There are many small waterfalls upstream in the dense woods, which repeat the travertine formation effect. The city of Davis now owns thousands of acres of this land and has made it a tourist attraction. Another travertine visage lies in Sulphur, Oklahoma, just 10 miles east of Turner Falls. Travertine Creek flows through a spring water nature preserve within the boundaries of the Chickasaw National Recreation Area. In Texas, the city of Austin and its surrounding "Hillcountry" to the south is built on limestone and is home to many travertine formations such as those found at Gorman Falls within Colorado Bend State Park, the nature preserve known as Hamilton Pool, the nature preserve known as West Cave Preserve and a nature spot in Spicewood known as Krause Springs. Uses , 1000 years old and mainly built with travertine]] Travertine is often used as a building material. Rich deposits of aged, dried and hardened travertine were mined by the Romans. The largest building in the world constructed mostly of travertine is the Colosseum in Rome. Other notable buildings using travertine extensively include the Sacré-Cœur Basilica in Paris and the Getty Center in Los Angeles, California. The travertine used in the Getty Center construction was imported from Tivoli and Guidonia.The Getty Center http://www.getty.edu/visit/see_do/architecture.html Travertine is one of several natural stones that are used for paving patios and garden paths. It is sometimes known as travertine limestone, sometimes as travertine marble; these are the same stone, even though travertine is not a type of marble. The stone is characterised by pitted holes and troughs in its surface. Although these troughs occur naturally, they suggest to some eyes that have undergone considerable wear and tear over many years. Some installers use a grout to fill these holes, whereas others leave them open — travertine can even be purchased "filled" or "unfilled." It can be effectively polished to a smooth, shiny finish and comes in a variety of colors from grey to coral-red. Travertine is most commonly available in tile sizes for floor installations. Travertine is one of the most frequently used stones in modern architecture, and is commonly seen as façade material, wall cladding, and flooring. The lobby walls of the modernist Willis Tower (formerly Sears Tower) in Chicago, Illinois are travertine.The Willis Tower http://www.willistower.com/interior_exterior.html Architect Welton Becket was one of the most frequent users of travertine, incorporating it extensively into many if not most of his projects. The entire first floor of the Becket-designed UCLA Medical Center has thick travertine walls. Architect Ludwig Mies van der Rohe has used travertine in two of his major works, S.R. Crown Hall and the Farnsworth house. The relative softness of the stone, combined with the holes and troughs, make travertine flooring particularly difficult to finish and maintain. Aggressive grinding — sometimes called honing — can reveal previously hidden air pockets that significantly change the look of the floor. There are two or three small travertine producers in the western United States. U.S. demand for travertine is about 0.85 million tons, almost all of it imported. Most of the imports come from Turkey, Mexico, Italy, and Peru. A decade ago, Italy had a near monopoly on the world travertine market. See also * Calc-sinter * Karst topography References External links *New Mexico travertine study *Minerals.net Aragonite Category:Sedimentary rocks Category:Limestone Category:Springs ca:Travertí cs:Travertin da:Frådsten de:Travertin es:Travertino eo:Travertino eu:Trabertino fa:تراورتن fr:Travertin gl:Travertino io:Travertino it:Travertino lt:Travertinas li:Travertin nl:Travertijn ja:トラバーチン no:Travertin pl:Trawertyn pt:Travertino ro:Travertin ru:Травертин simple:Travertine sk:Travertín sl:Lehnjak fi:Travertiini sv:Travertin tr:Traverten uk:Травертин